The present invention relates to an extended interaction microwave oscillator.
Such extended interaction oscillators are well known from the prior art.
These oscillators are particularly used towards millimetric wavelengths as measuring oscillators or heterodyne radar transmitters and receivers. They comprise a relatively short line section with a periodic structure, being in general only constituted by about 10 identical stages. This line generally comprises a succession of metal bars and slots or a sequence of identical or non-identical metal vanes (rising sun-type structure). This line section is contained in a vacuum-tight case.
A linear electron beam passes through the line or lightly touches it, whilst an extremely high frequency wave is produced which is propagated in the case. Interaction takes place between wave and beam and the line-case assembly resonates. Oscillation generally takes place on the .pi. mode.
The prior art extended interaction oscillators have the following disadvantages. The mechanical tolerances for the periodic structure line are very strict. In fact it can be considered that the extended interaction oscillator comprises a sequence of resonant cavities. It is very important that these cavities have precisely the same geometrical structure, particularly to prevent spurious oscillations making very strict mechanical tolerances necessary, particularly for the line. Extended interaction oscillators can be mechanically tuned in a relatively small frequency band. The various oscillation modes are very close to one another and random mode jumps occur. Thus, the quality of the frequency spectrum produced is not very good and this deteriorates as the overvoltage decreases. Due to this low overvoltage the losses are significant and the efficiency relatively poor.